A student models the diffusion of glucose across a section of the small intestine.
The student calculates a relative diffusion value using
relative diffusion value=surface area×concentration differencemembrane thickness \text{relative diffusion value}=\frac{\text{surface area}\times\text{concentration difference}}{\text{membrane thickness}} relative diffusion value=membrane thicknesssurface area×concentration difference| Factor | Value |
|---|---|
| surface area | 48 mm2 |
| concentration difference | 3.0 mmol dm−33.0\,\mathrm{mmol\,dm^{-3}}3.0mmoldm−3 |
| membrane thickness | 0.024 mm |
Calculate the relative diffusion value for this section of the small intestine.
Blood flowing past this section carries absorbed glucose away.
Explain why this blood flow increases the rate of glucose diffusion.
102 exam-style questions on Edexcel GCSE Biology 8.1 Exchange surfaces and diffusion, covering 8.1.1 Introduction to exchange and transport, 8.1.2 Alveoli adapted for gas exchange, 8.1.3 Factors affecting rate of diffusion, and 8.1.4 Rate of diffusion using Fick's law. Each one has a worked solution and a mark scheme showing where the marks go.